Image acquired February 19, 2010: Tropical Cyclone Gelane had sustained winds of 125 knots (230 kilometers per hour) and gusts up to 150 knots (275 kilometers per hour), according to a report from the U.S. Navyâs Joint Typhoon Warning Center (JTWC) on February 19, 2010. The JTWC reported that Gelane was roughly 315 nautical miles (585 kilometers) east-northeast of Port Louis, Mauritius, and was forecast to travel toward the southwest, weakening slightly as it moved.
The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASAâs Aqua satellite captured this true-color image on February 19, 2010. Gelaneâs spiral arms span hundreds of kilometers over the open ocean.
Credit: NASA image by Jeff Schmaltz, MODIS Rapid Response Team, Goddard Space Flight Center. Caption by Michon Scott.
Instrument:Â Aqua - MODIS
For more details and a higher res file of this image go to:
http://earthobservatory.nasa.gov/NaturalHazards/view.php?id=42767

In recent years, the Middle East and South Asia have been hit by several very destructive storms. While the region is often beset by such occurrences, a new study believes that air pollution caused by soot and aerosol emissions in developing countries is making cyclones much more destructive. The study, that was published in Nature magazine last week, stated that emissions caused by burning fossil fuels ‘interfere’ with wind patterns and, as a result, reduces wind shear. This allows cyclones to grow in size and become more destructive, when wind shear would normally ‘tear them apart’ when they reach a certain size.

The research team compared cyclones that occurred between 1979 and 1996 with those between 1997 and 2010 and found that the more recent ones were up to 3x stronger. Not only were wind speeds stronger, but wind shear was much lower. They also discovered that aerosol emissions in the two regions had grown by a factor of six since the 1930s, causing a three-kilometer-thick layer of pollution over the Indian Ocean, known as the South Asian atmospheric brown cloud. This cloud absorbs sunlight, causing the ocean to cool and affecting wind circulation.

Scientists have long theorized that pollution had effected the monsoon season, but this is the first time that a connection to more destructive storms has been put forward. Speaking to SciDev.Net, Amato Evan, lead author of the study said: “I would say that the effect on cyclones is very strongly linked to the well-known effect of these aerosols on the monsoon circulation and rainfall; that is, their propensity to weaken the monsoon circulation and reduce rainfall.”

“We are showing that pollution from human activity — as simple as burning wood or driving a vehicle with a diesel engine — can actually change these massive atmospheric phenomena in a significant way. It underscores the importance of getting a handle on emissions in the region.”

“If you live in an area where these very strong cyclones can make landfall, this effect [the destruction due to the cyclone] is absolutely significant,” Evan added. “The historical tropical cyclones in the Arabian Sea that were very intense made landfall in India, Pakistan, Oman, and Iran, in each case with tremendous destruction and loss of life.” So air pollution can not only cause respiratory illnesses, but also destructive cyclones.